1. Field of the Invention
The present invention relates to a method for forming fine resist patterns, in particular, a method for forming fine resist patterns to semiconductors, ICs, bubble memories and the like by performing a dry resist development process.
2. Description of the Prior Art
Hitherto for the formation of fine resist patterns to semiconductors, the following steps have been carried out:
(a) A resist prepared by dissolving an organic high-polymer in a solvent is spin-coated on the substrate.
(b) The coated film is dried.
(c) The dried film is exposed to light or radiations such as electron beam, X-rays, .alpha.-rays, or ion beams.
(d) A pattern is formed by a wet development process utilizing the difference of solubility to a solvent between the part exposed to light or radiations and the part not exposed.
However, the above mentioned method have some problems that a large amount of solvent is required; in the course of forming a pattern by development the pattern swells with the solvent to spoil the dimensional accuracy; the sensitivity of resist itself is made not uniform; and the sensitivity lowers due to a change with the passage of time.
Besides, the dry lithography is known, which prepares a resist film by plasma polymerization and forms a resist pattern by oxygen plasma development (J. Appl. Phys. vol. 51, p. 3938, 1980).
However, in the above mentioned method the sensitivity has been poor and the ratio of film thickness of the part remaining as a pattern after the development to the film thickness before the development (hereafter called the residual film ratio) is in the extent of 10 to 15%, at best 50 to 60%, so that it has been difficult to obtain a film thickness bearable to the subsequent selective etching (Japanese Patent Laid-open No. 72175/'77).